The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.
Conventional techniques for detecting obscured targets employ some form of xe2x80x9chuman intelligencexe2x80x9d where xe2x80x9ca priorixe2x80x9d information is gathered over a period of time by one of the intelligence agencies. If a threat is detected as a result of these intelligence gathering procedures, military or paramilitary forces are often employed at the risk of injury. In extreme cases even loss of life may be incurred. Also, expensive equipment may become severely damaged or unrecoverable.
On the technology forefront, advanced Automatic Target Recognition (ATR) research in the last decade or so has been focused on developing Synthetic Aperture Radar (SAR) and Electro-Optics (EO) along with other imaging technologies for specific reconnaissance and surveillance platforms. Recent advances have lead to a limited number of automated techniques for detecting targets in open terrain and over a limited number of benign conditions. For situations that require the detection of obscured targets, recent initiatives such as development efforts for Foliage Penetration (FP) and Ground Penetrating Radar (GPR) show promise as future technologies to detect targets within forest clutter and obtain signal information from underground facilities, respectively. At present, these technologies have a great deal of scope for further development and are not fully mature for even initial implementation. Realistic possibilities for near-term exploitation of these technologies require a considerable amount of human-in- the-loop intervention to combine information from a variety of sources.
Most existing approaches to advanced airborne sensor research, as briefly described in the previous paragraph, operate at a considerable stand-off range. By contrast, the system concept of the invention uses xe2x80x9csmartxe2x80x9d or xe2x80x9croboticxe2x80x9d low-altitude UAV""s with on-board processing capabilities that allow the small UAV to adaptively self-position or converge to a region-of-interest that, for example, contains obscured targets via the deployment of relatively inexpensive platforms without exposing personnel to dangerous situations. Potential applications include important military as well as environmental monitoring scenarios.
This low-altitude xe2x80x9croboticxe2x80x9d UAV technology has important applications for emerging and future threat scenarios in hard urban environments where, for example, xe2x80x9cobjects of interestxe2x80x9d may be concealed between buildings as well as other challenging environments such as, for example, surveillance and interrogation of regions-of-interest that may be embedded within mountainous terrain. The multi-static radar UAV system concept of the invention utilizes unmanned low-altitude xe2x80x9croboticxe2x80x9d UAV sensors that provide intelligence information for these challenging emerging and future threat environments.
Specifically, the present invention provides a new bistatic/multistatic radar system concept for purposes of interrogating difficult targets with low-altitude xe2x80x9csmartxe2x80x9d or xe2x80x9crobotic-typexe2x80x9d UAV platforms. One of the novel aspects is the development of a UAV system concept that implements self-adaptive positional adjustments based on sensed properties of the propagation channel. This aspect is based on signal differential path length analysis for purposes of isolating regions where targets are potentially obscured and difficult to detect via conventional techniques.
A new bistatic radar concept utilizing a high-altitude UAV that works in tandem with a group of low-altitude UAVs. The concept is divided into a position-adaptive bistatic mode and a close-range monostatic mode. In position-adaptive (robotic) bistatic mode, each low-altitude UAV estimates a new parameter denoted as the differential path length to adaptively implement self-adjustments in position. This approach provides each UAV with the potential for looking down the xe2x80x9cthroatxe2x80x9d of an obscuration channel. In the event that a particular low-altitude UAV detects an obscuration channel, the low-altitude UAV will transfer to a close-range monostatic mode in an effort to interrogate the obscuration channel for targets.
It is therefore an object of the invention to provide a multi-static radar system concept for interrogating difficult targets with low-altitude xe2x80x9csmartxe2x80x9d UAV platforms.
It is another object of the invention to provide the capability to isolate regions where targets are potentially obscured and difficult to detect via conventional techniques.
It is another object of the invention to provide interrogation of difficult and obscured targets via the deployment of relatively inexpensive platforms without exposing personnel to dangerous situations.
It is another object of the invention to provide a UAV system concept that implements self-adaptive positional adjustments based on sensed properties of the propagation channel.
These and other objects of the invention described in the description, claims and accompanying drawings are achieved by multi-mode, radar method for detecting targets in difficult and obscured environments comprising the steps of:
transmitting a signal through a channel from a high altitude unmanned air vehicle;
passively receiving said signal from said transmitting step through a plurality of unmanned air vehicles at a low altitude platform relative to said unmanned air vehicle from said transmitting step,
determining a differential signal time delay from a time said signal is transmitted at said transmitting step and a time said signal is received at said receiving step, said differential time delay indicating a differential time path obstruction between said high altitude unmanned air vehicle and said unmanned air vehicle at said low altitude platform;
monitoring said signal time delay by said low altitude platform unmanned air vehicles and converging to a point that corresponds to a minimum time delay; and
detecting targets within said differential time path at said point of minimum time delay by an unmanned air vehicle at a low altitude platform.